STEP 2. UNDERSTAND YOUR SOIL
Soil composition influences the fertility of the soil and its water holding capacity amongst other properties. Anyone who has tried to build a moat around a sand castle knows that sand does not hold water. The large soil particles let water drain straight through the profile. Conversely, try walking over a clayey field in winter and you'll end up bringing most of it home with you on your boots! Clay soils hold on to moisture. Silty soils are reasonably moisture retentive but, like clay, compact easily due to their small particale size, so can be difficult to work until they dry out. Clay soils bind to nutrients better than silty soil, whilst sandy soils have poor nutrient retention.
There is a very simple and quick test to determine what your soil type is. Collect a handful of soil from your garden and rub it between your fingers. If it is gritty, then it is a sand, especially if you moisten it and it will not form a ball. Clay soil feels smooth between your fingers and forms balls readily. A silty soil feels soapy and doesn't form a ball as easily as clay does.
Knowing what kind of soil you have in your garden helps you to plan what plants to grow, how much water and nutrients to apply, and whether you need to improve your soil's nutrient and water holding capacity by adding organic matter in the form of well composted manure, leaf mould or garden compost.
What type of soil you have is important as it is where your plants are going to get their nourishment from. Some plants prefer particular soil types and it will usually tell you in the plant description.
Plants for different soil types
Chalk
Chalky soils (or those based on limestone) are usually alkaline, so have a pH above 7. They tend to be freely draining, stony and don't hold on to nutrients very well. Therefore, to help your plants flourish, you should water regularly and dig in lots of composted organic matter as often as you can.
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Clay
Clay soil is usually rich in nutrients, but it can be hard to dig, and if it is very heavy, it can hold wter for long periods of time. It may also take a long time to warm up in spring, which can slow down the new growth. If your clay soil is badly compacted, you can help improve the structure by digging in lots of sharp sand and composted organic matter.
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Sand
Sandy soils tend to drain very quickly, so are ideal for supporting Mediterranean-style or drought-tolerant plants, which are happiest in dry conditions. These soils are usually low in nutrients, so digging in lots of composted organic matter will not only bump these up, but will also help it retain water.
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Improving soil quality
It is possible to improve your soil. The usual way is with the addition of multi-purpose compost when you are preparing the ground for planting. Heavy clay soil can also benefit from the addition of sand or grit which improves drainage so plant roots don't get waterlogged and rot.
Shop compostA BIT ABOUT ACIDIC PLANTS AND ERICACEOUS COMPOST
pH testing
Some plants like an acidic soil. These plants which are acid-loving are also referred to as ericaceous plants. Common examples are camellias, azaleas, rhododendrons, and blue hydrangeas. If you specifically want to grow these plants and you know your soil is not acidic, then you can add ericaceous compost when you plant them. You will continue to need to feed the plants with ericaceous nutrients (in plant feed and topping up with compost). It is easier to plant them in pots where you can better control the nutrient mix to ensure these plants stay healthy and looking their best.
Soil test kit
Soils are further divided into alkaline and acidic depending on the behaviour of hydrogen ions in the soil which are measured as pH (potential hydrogen and is an indicator of how active the hydrogen is). All gardeners need to know the pH of their soils as plants are grouped into acid loving and non-acid tolerant. If you grow acis loving plants like camellias or rhododendrons on an alkaline soil, they will eventually die as the soil chemistry will not allow the plants to absorb all the nutrients that they need to live.
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